In the event of some fault occurring in a vehicle while the vehicle is being driven, it has heretofore been customary for an electronic control unit (hereinafter referred to as “ECU”) on the vehicle which deals with the faulty component to record fault information such as a fault code or the like. If a serious fault such as a fault with respect to an engine combustion or exhaust system of the vehicle occurs, it has been the practice to turn on a warning lamp on the instrument panel to let the driver know the occurrence of the fault.
For example, if an engine coolant temperature sensor of the vehicle fails, then an engine ECU records a fault code “PXXXX” and turns on a PGM-FI warning lamp to indicate the fault to the driver.
For repairing the vehicle, the repair shop worker connects an external diagnosing apparatus to a data link connector of the vehicle, and reads fault codes accumulated in the engine ECU, which is an ECU concerned with engine coolant temperature faults, to confirm or recognize details of the failure. Therefore, the repair shop worker can spot the location and cause of the failure relatively easily.
Attempts have been made to let the driver of a vehicle know its states in combination with a system, known as an idling stop control system, that automatically stops the engine of the vehicle from idling when the vehicle comes to a halt based on an overall judgment made in view of various factors including a reduction in fuel consumption. The idling stop control system judges whether the engine should be stopped from idling or not, using various ECUs that cooperatively judge merits and demerits of the engine stopped from idling. When the engine is stopped from idling by the idling stop control system, the fact that the engine is stopped from idling is displayed on an instrument panel, making the driver rest assured at the time the vehicle stops moving (see, for example, Abstract of Japanese Laid-Open Patent Publication No. 2004-224269).